The present invention relates generally to removing material from a body of the same or dissimilar material. More particularly, the present invention concerns the controlled removal of material utilizing cavitationally induced material erosion.
The phenomenon of cavitation of dynamic fluid systems is not new. Cavitation and the associated erosion has been treated as a problem that is common to many complex engineering applications. Typically, cavitation is a phenomenon which is to be avoided because it results in rapid deterioration and failure of adjacent solid surfaces. To be sure, there have been attempts to use the destructive characteristics of cavitation to accomplish a useful purpose. For example, cavitating fluid flows have been used in order to drill holes through comparatively solid material. See, for example, U.S. Pat. No. 3,528,704 issued to Johnson, Jr. Moreover, the task of drilling with a nonsubmerged cavitating jet surrounded by a fluid sheath, has also been considered. See, for example, U.S. Pat. No. 3,807,632 issued to Johnson, Jr.
The cavitation phenomena has also been used generally in bore hole drillings for removal of mineral deposits far below the earth surface. See, for example, U.S. Pat. No. 3,603,410 issued to Angona, U.S. Pat. No. 3,545,552 issued to Angona and U.S. Pat. No. 3,387,672 issued to Cook. The more conventional rotary drilling techniques in bore hole drilling have been used with an artificially induced cavitational flow in the form of evacuated capsules to cavitationally augment the rotary drilling process. See, for example, U.S. Pat. No. 3,174,561 issued to Sterrett.
The known approaches to cavitationally augmented drilling techniques are, however, fraught with numerous problems. For example, the known devices for drilling are not adapted for other material removing functions such as cutting, cleaning, trenching and the like. Similarly, the known devices operate very inefficiently and have massive input power requirements. In another vein, known cavitational processes do not exhibit the ability to selectively remove one material from a second material. Such problems as those enumerated above are of particular importance when one considers the problems such as removal of boiler scale without disassembling the boiler, the cleaning of large surfaces such as runways, and removal of marine growth from seagoing vessels without dry docking the vessel.
In conventional apparatus for drilling, cutting and cleaning a material, there is mechanical interaction between the tool of the apparatus and the material. Such mechanical interaction either limits the useful life of the tool or results in a reduction in the useful life of the tool. This life reduction is directly attributable to the mechanical wear induced by friction between the material and the tool. To avoid such deleterious interaction, it is necessary to decouple the cutting element from the material.
In addition to the problems discussed above, the prior art cavitational devices require massive input power sources, use large flow rates of the cavitating medium, have unacceptably slow material removal rates and generally fail to appreciate and utilize the full potential of a cavitating flow system.
In view of the foregoing discussion, it will be apparent that the need continues to exist for a truly effective cavitational system for removing material which is capable of performing such machining functions as cutting, drilling and cleaning.